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Targeting leg fatigue in heart failure

Published Monday 31 October 2011

Doctors should not only treat the heart muscle in chronic heart failure patients, but also their leg muscles through exercise, say researchers in a major new study.

Heart failure causes breathlessness and fatigue that severely limits normal daily activities such as walking. The University of Leeds research team has, for the first time, shown that leg muscle dysfunction is related to the severity of symptoms in heart failure patients. These findings suggest that daily activity in patients with severe heart failure may not simply be limited by the failing heart, but also by an impairment in the leg muscles themselves.

In a series of experiments with chronic heart failure patients, the research team measured responses of the heart, lungs and leg muscles following a moderate exercise warm-up. Using a near-infrared laser to measure the oxygenation of the leg muscles, they found that warm-up exercise increased the activity of skeletal muscle enzymes that control energy production. However, this adaptation was less in patients with the most severe symptoms, showing that the heart failure condition had a negative impact on the normal function of the leg muscles.

Dr Harry Rossiter, of the University's Faculty of Biological Sciences says: "Many chronic heart failure patients complain of leg fatigue during exercise and this can prevent them from being active. Our study shows that by warming up properly, patients can improve the oxygenation and performance of their leg muscles, which is beneficial in promoting exercise tolerance."

"When your muscles don't use oxygen well, it causes an uncomfortable burning sensation during activity," says Dr Klaus Witte, the Leeds General Infirmary Cardiologist on the research team. "The effect of a warm up is to direct oxygen to the places that are going to need it, and make the muscles ready to use it when you start exercising."

Dr Rossiter says the next stage of this research will be to see whether training of the skeletal muscles can improve long-term overall outcomes for patients with chronic heart failure, and to discover more about the pathological changes in the leg muscles that may be a contributing factor in limiting exercise.

"Our main message is that exercise is safe and beneficial in patients with heart failure. By warming up the leg muscles properly, the exercise can be more comfortable and sustained for longer - affording great benefits for these patients," he says.

This study is published in the Journal of Applied Physiology in a paper entitled The intramuscular contribution to the slow oxygen uptake kinetics during exercise in chronic heart failure is related to the severity of the condition. http://jap.physiology.org/

The full paper is available from Campus PR or the University of Leeds press office on request.

The Faculty of Biological Sciences at the University of Leeds is one of the largest in the UK, with over 150 academic staff and over 400 postdoctoral fellows and postgraduate students. The Faculty is ranked 4th in the UK (Nature Journal, 457 (2009) doi :10.1038/457013a) based on results of the 2008 Research Assessment Exercise (RAE). The RAE feedback noted that "virtually all outputs were assessed as being recognized internationally, with many (60%) being internationally excellent or world-leading" in quality. The Faculty's research grant portfolio totals some £60M and funders include charities, research councils, the European Union and industry. www.fbs.leeds.ac.uk

The University of Leeds is one of the largest higher education institutions in the UK with more than 30,000 students from 130 countries. With a turnover approaching £450m, Leeds is one of the top ten research universities in the UK, and a member of the Russell Group of research-intensive universities. It was placed 80th in the 2007 Times Higher Education world universities league table. The University's vision is to secure a place among the world's top 50 by 2015. www.leeds.ac.uk

Leeds General Infirmary (LGI) is part of the Leeds Teaching Hospitals NHS Trust, one of the largest NHS organisations in the UK. The LGI is home to the Yorkshire Heart Centre, which treats patients from across West Yorkshire, North Yorkshire and beyond and has an excellent clinical and research reputation.